The present disclosure relates to earth-penetrating drill bits and, more particularly, to rolling cutters that can be used in drill bits.
Wellbores for the oil and gas industry are commonly drilled by a process of rotary drilling. In conventional wellbore drilling, a drill bit is mounted on the end of a drill string, which may be several miles long. At the surface of the wellbore, a rotary drive turns the drill string, including the drill bit arranged at the bottom of the hole to increasingly penetrate the subterranean formation, while drilling fluid is pumped through the drill string. In other drilling configurations, the drill bit may be rotated using a mud motor arranged axially adjacent the drill bit in the downhole environment and powered using the circulating drilling fluid.
One common type of drill bit used to drill wellbores is known as a “fixed cutter” or a “drag” bit. This type of drill bit has a bit body formed from a high strength material, such as tungsten carbide or steel, or a composite/matrix bit body, having a plurality of cutters (also referred to as cutter elements, cutting elements, or inserts) attached at selected locations about the bit body. The cutters may include a substrate or support stud made of carbide (e.g., tungsten carbide), and an ultra-hard cutting surface layer or “table” made of a polycrystalline diamond material or a polycrystalline boron nitride material deposited onto or otherwise bonded to the substrate. Such cutters are commonly referred to as polycrystalline diamond compact (“PDC”) cutters.
In fixed cutter drill bits, PDC cutters are typically located within corresponding cutter pockets defined within blades that extend from the bit body, and can be bonded to the blades by brazing to the inner surfaces of the cutter pockets. The PDC cutters are positioned along the leading edges of the blades of the bit body so that rotating the bit body results in the PDC cutters engaging the rock to penetrate the underlying formation. In use, high forces are exerted on the PDC cutters, particularly in the forward-to-rear direction. PDC cutters are typically fixed to the bit body such that a common cutting surface contacts the formation during drilling. Over time, however, the edge of the working surface of the PDC cutter that constantly contacts the formation can wear down or dull, which can result in longer drill times due to a reduced ability of the drill bit to effectively penetrate the formation.